The present invention pertains to a method of mounting and aligning an endless belt on associated rollers in a machine. More particularly, the present invention relates to a method and device for facilitating installation of an endless belt, such as a photoconductive belt, into an electrostatographic printing machine.
A typical electrostatographic printing machine 10 is diagrammatically illustrated by way of example in FIG. 1. Printing machine 10 includes a photoconductive member 10 in form of an endless photoconductive belt 12 having a photoconductive surface 14. The photoconductive belt is mounted on a plurality of guide rollers 16 and backer bars 18. At least one of the rollers 16 is driven for rotating the belt in the direction of arrow 20 through a plurality of generally conventional electrostatographic printing modules. First, a charging module 22 charges the photoconductive surface 14 of the belt 12 to a substantially uniform potential. An exposing module 24 then exposes the charged photoconductive surface to a light image of an original document being reproduced. Exposure of the charged photoconductive surface 14 selectively dissipates the charge in the irradiated areas of the photoconductive surface. As a result, an electrostatic latent image corresponding to the image of the original document is formed on the photoconductive surface 14. After the electrostatic latent image is recorded on the photoconductive surface, a developing module 26 develops a latent toner image on the photoconductive surface by bringing a developer material into contact with the photoconductive surface. In typical bi-component developer systems, the developer material is composed of toner particles adhering triboelectrically to carrier granules. The toner particles are attracted from the carrier granules to the latent image to form a developed toner image on the photoconductive member. The toner image is then transferred from the surface of the photoconductive member 10 to a copy substrate or print sheet 30, such as a sheet of paper, by a transfer module 28. Thereafter, heat or some other known treatment is applied to the toner image on the print sheet by a fuser 32, thereby permanently affixing the toner image to the print sheet. Residual toner is removed from the photoconductive member by a cleaner 34.
In order to generate multi-color prints, there may be a group of process modules 22, 24, 26 through 22-C, 24-C, 26-C for each of a plurality of colors. For example, there may be a group of modules for each of cyan 22, 24, 24, 26, yellow 22-A, 24-A, 26-A, magenta 22-B, 24-B, 26-B and black 22-C, 24-C, 26-C. There may also be one or more additional sets of modules 22-D, 24-D, 26-D for one or more custom colors. One method of generating multicolor prints is to arrange all of the color modules around a single photoreceptor belt 12 as illustrated in FIG. 1. The full color image may be formed by exposing and developing all of the color toner images, one on top of each other, during a single rotation of the photoreceptor belt. The full color toner image may then be transferred from the photoreceptor belt directly to a print sheet.
An alternative method of generating full color prints is to expose and develop each individual color image on the photoreceptor belt 12 separately, and transfer the single color toner image to an intermediate transfer belt (not shown) before exposing and developing the next color toner image. This is repeated for each color, thereby building up a full color toner image on the intermediate transfer surface. The full color toner image is then transferred from the intermediate transfer surface to the print sheet. The intermediate transfer surface may be formed on an intermediate transfer belt, roll, drum or other suitable structure.
The electrostatographic printing processes described above are well known and are commonly used for light lens and digital reproduction of an original document. In each of the above described methods, four or more sets of discharging 22, exposing, 24 and developing 26 modules are spaced around the photoreceptor belt 12 in order to generate a full color image. The photoreceptor belt must be relatively large in order to accommodate all of the reprographic modules around its periphery. Such a photoreceptor belt may, for example, have a circumference of about 2.8 meters. The ability of the photoreceptor belt 10 to obtain and retain the desired charges degrades over time. As a result, the photoreceptor belt requires regular replacement to maintain optimal performance of the machine. The relatively large photoreceptor belt required for the full color machines described above is cumbersome to handle due to its size and weight.
Referring now to FIGS. 2 and 3, in existing machines the guide rollers 16 and backer bars 18 may be mounted on a photoreceptor sub-frame 40. The sub-frame may include an outboard plate 42 and an inboard plate 44, with the guide rollers and backer bars being mounted for rotation between the plates 42 and 44. The sub-frame may be mounted to the machine frame (not shown) on slides (not shown). With this construction, the sub-frame may be undocked form the machine frame and slid partway out of the machine frame, in order to facilitate access thereto for maintenance, such as photoreceptor belt replacement. Some of the rollers and/or guide plates may be moved into a retracted position (not shown), i.e. radially inward relative to the belt (not shown in FIG. 2), such that the overall peripheral circumference defined by the guide rollers and backer bars is reduced. This provides some slack in the photoreceptor belt 12 during belt installation and removal of the belt, thereby facilitating installation and removal of the belt.
Once installed, the photoreceptor belt 12 is maintained in proper alignment in an optimum position on the guide rollers 16 by a steering mechanism. The steering mechanism typically includes a belt edge sensor 46 for determining the location of the inboard edge 52 of the photoreceptor belt in a known manner. One known type of suitable sensor emits an output voltage that varies depending on the detected location of the inboard edge 52 of the photoreceptor belt. The further inboard the edge of the belt moves, the higher the magnitude of the output voltage emitted by the belt edge sensor becomes.
When the output voltage of the sensor deviates from an acceptable range of voltages, then the steering mechanism steers the belt back toward its optimum position, until the belt edge sensor output voltage is back within the acceptable range. In order to steer the belt 12 in the inboard or outboard direction as required to move the belt back within an acceptable range of the optimum position, one of the rollers, a steering roller 48, is pivoted by a stepper motor 50, or other suitable means (not shown).
When installing a photoreceptor belt 12 in existing machines, the operator must first manually place the inboard edge 52 of the photoreceptor belt 12 over the guide rollers 16 and backer bars 18, as shown in FIG. 3. Care must be taken to clear the edges of the rollers, backer bars and other components on or near the outboard plate 42 of the photoreceptor sub-frame 40, in order to avoid damaging the photoreceptor belt 12. Once these components are cleared, the photoreceptor belt is slid further onto the rollers and backer bars, until the inboard edge 52 of the photoreceptor belt contacts and begins to activate the belt edge sensor 46. The operator now checks the output voltage of the belt edge sensor to determine if the photoreceptor belt is within the effective range of the steering mechanism. The steering mechanism""s effective range of operation may be, for example, +/xe2x88x921 mm of the ideal position for the photoreceptor belt. The operator typically checks to see if the belt is within this range by attaching a volt-meter (not shown) to contacts (not shown) provided for this purpose on the photoreceptor sub-frame 40 or elsewhere on the machine. The operator then checks the volt-meter to see of the belt edge sensor output voltage is within the acceptable range. If not, then the operator must then manually slide the photoreceptor belt in or out slightly, until the belt edge sensor output voltage is within the acceptable range.
The above described installation process entails much physical handling of the photoreceptor belt 12. The Operator must initially place the photoreceptor belt on the photoreceptor sub-frame 40 without catching the edge or surface of the belt on any part of the photoreceptor sub-frame, which would result in damaging dings and/or scratches in the photoreceptor belt. When installing a relatively large photoreceptor belt, it is difficult to perform this feat without damaging the photoreceptor. Next, the operator must slide the photoreceptor belt into contact with the belt edge sensor 46. In order to slide the belt into place on the photoreceptor sub-frame, the operator must place her hands on the photoconductive surface 14 of the belt and push inward on the belt. Physical contact with the photoconductive surface of the belt degrades this critical surface and must be minimized. Once in this rough position, the operator must push and pull on the belt, again by contacting the photoconductive surface of the belt, until the output voltage of the belt edge sensor is within the acceptable range. During this process, should the belt be accidentally slid too far inward against the belt edge sensor or other components of the photoreceptor sub-frame, then the inboard edge of the belt may be damaged.
Since the photoconductive surface 14 of the belt 12 is sensitive to light, it must be installed on the photoreceptor module relatively quickly, in order to minimize exposure of the belt to light. Prolonged exposure of the photoreceptor belt to the light overly discharges or xe2x80x9clight shocksxe2x80x9d the photoconductive material and shortens the useful life of the belt. As result, when installing a photoconductive belt 12 as described above, the operator is necessarily in a hurry to avoid harmful prolonged exposure the photoconductive belt to the light. The combination of being in a hurry and having to accurately locate the inboard edge of the photoreceptor belt up against an edge sensor within a 2 millimeter range creates an unacceptably high likelihood of accidentally xe2x80x9cdingingxe2x80x9d or scratching of the photoconductive surface 14 of the belt 12.
There is a need in the art for an improved method and apparatus for installing a photoreceptor belt 12 in an electrostatographic printing machine. There is a need for such an improved method and apparatus that minimizes the handling of the belt by the operator, so that the chances of accidentally damaging the belt due harmful contact with the photoconductive surface of the belt are minimized. There is also a need in the art for a faster method and apparatus for installing a photoreceptor belt in a machine, such that exposure to light and handling of the belt can both be minimized.